JPS6336534A - Cleaning equipment - Google Patents

Abstract

PURPOSE:To remove effectively fine contaminant attaching to a surface, and prevent the generation of damage on the surface of a body to be treated, by assembling a vibrating plate of high melting point metal and an oscillator, and applying effectively ultrasonic waves in a specified range of frequency to the cleaning liquid in a cleaning tank. CONSTITUTION:A 0.1-0.5mm thick rectangular vibrating plate 6 made of tanta lum is arranged between the upper surface of a base stand 1 and the base surface of a cleaning tank 3. On the base stand 1 side surface of the vibrating plate 6, fourteen pieces of hexagonal vibrators 10 are arranged and fixed so as to closely approach with each other. These vibrators 10 are connected, via a lead plate 11 and a cable 12, to an oscillator 13 which generates hight fre quency at 400-1000kHz and performs a sweep of +2.5kHz width. The vibrators exhibit some irregularity of vibration characteristics depending on the form, the film thickness, etc. The oscillator 13, however, can resolve the decrease of oscillation efficiency caused by the irregularity of vibration characteristics between each vibrator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cleaning device, and in particular to a cleaning device suitable for cleaning semiconductor wafers, metal magnetic disks, etc. that require high cleanliness. Technology] One of the manufacturing processes for semiconductor devices is a cleaning process.

This cleaning utilizes the etching action of the semiconductor wafer by a cleaning solution to: 1) remove the contaminant layer on the wafer surface to create a clean surface; 2) finish the wafer surface smooth; 2) etch the wafer to a predetermined thickness and shape. This is done to achieve the following objectives.

By the way, conventionally, semiconductor wafers have been cleaned by using an apparatus containing a heated cleaning liquid in a cleaning tank, and by immersing a plurality of wafers housed in a cassette in the cleaning liquid. There is. However, when such a cleaning device is used, it is difficult to obtain a highly clean wafer because many of the contaminants on the wafer surface are chemically insoluble in the cleaning solution. Furthermore, the lifetime of the cleaning liquid is short, and the cleaning performance becomes unstable due to the generation of numerous bubbles. Furthermore, there is a problem in that cleaning liquid or the like stagnates on the contact surface between the cassette and the wafer, deteriorating the cleaning effect of the wafer near the contact surface.

For this reason, a stainless steel diaphragm with a thickness of 2 to 3 mm was placed at the bottom of the cleaning tank containing the cleaning solution so as to be in direct contact with the cleaning solution, and the 28kHz frequency was set on the diaphragm.
A cleaning device having a structure equipped with a vibrator that is supplied with a frequency of ~200 kHz has been developed.

According to such a cleaning device, the above-mentioned problems can be solved. However, the cleaning device described above can only remove contaminants of several micrometers or more, and it is difficult to remove even finer contaminants of 0.3 μm.

Further, when ultrasonic waves are applied to the cleaning liquid via a vibrator and a vibration plate that vibrate at the above-mentioned frequency, it has been reported that damage to the wafer surface is caused by the caviar yong.

Furthermore, there is a problem in that contaminants gather on the wafer surface due to the dispersion and aggregation effects that are characteristic of ultrasonic waves.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned conventional problems.
The purpose of the present invention is to provide a cleaning device that can extremely effectively remove even minute contaminants and prevent damage to objects to be treated due to cavitation.

[Means and effects for solving the problem] The present inventors have discovered that a high-melting point metal has excellent chemical resistance, high tensile strength, and mechanical strength compared to stainless steel used in conventional diaphragms. Focusing on the fact that it can be made thin and has high vibration conversion efficiency in relation to the vibrator, we formed the diaphragm from the high-melting point metal, and defined the thickness of the diaphragm within a predetermined range. It has been found that by doing so, vibrations from a plurality of vibrators to which high frequencies of 400 to 1000 k)7z are applied can resonate well and provide ultrasonic waves of the same frequency to the cleaning liquid in the cleaning tank. In addition, by providing an oscillator with a function to sweep around a set frequency when vibrating multiple vibrators, it is possible to prevent vibrators with low vibration efficiency due to variations in the vibration characteristics of individual vibrators. It has been found that by sweeping with the oscillator, high-frequency vibrations of 400 to 1000 kHz can be efficiently applied to the diaphragm using these vibrators.

By incorporating the above-mentioned diaphragm, oscillator, etc., the present inventors were able to efficiently apply ultrasonic waves with a frequency of 400 to 1 [100 kHz to the cleaning liquid in the cleaning tank.
Furthermore, the fine particles (0
We have discovered a cleaning device that can effectively remove contaminants (up to 3 μm) and prevent damage to the surface of a processed object due to cavitation.

That is, the present invention includes a cleaning tank containing a cleaning solution, and a vibrator having a thickness of 0.0 L to 0.5 plate and is attached to the outer surface of this diaphragm, and is 400~1o
A plurality of vibrators vibrated at a high frequency of 00kHz,
This cleaning device is characterized by comprising an oscillator that vibrates these vibrators at the frequency and sweeps them in a range of ±LOOkHz or less around a set frequency.

Examples of high melting point metals for forming the diaphragm include tantalum, molybdenum, titanium, tungsten, and the like. In particular, tantalum is effective because it has superior high tensile strength compared to other high-melting point metals and has high vibration conversion efficiency in relation to the vibrator.

The reason for limiting the thickness of the diaphragm is that the thickness is 0,1
This is because if the thickness is less than u, the strength will not be maintained, whereas if the thickness exceeds 1.58, the resonance efficiency with the vibrator vibrating in the frequency range will decrease, and the vibration will be easily damped. A more preferable thickness of the diaphragm is 0.2 to 0.3
It is mm.

The reason for limiting the high frequency value given to the above vibrator is 4.
If the frequency is less than 10 kHz, fine contaminants attached to the surface of the workpiece cannot be effectively removed;
This is because if the frequency exceeds 00 kHz, the resonance efficiency of the diaphragm decreases due to the thickness of the diaphragm, and vibrations become more likely to be damped.

The above oscillator sweep conditions are ±100k of the set frequency.
It is necessary to keep it in the range of Hz or less, and a more preferable sweep width is ±15 kHz or less.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

1 in the figure is a base having a rectangular ring-shaped flange 2 on its upper part. A cleaning tank 3 made of polypropylene, for example, is installed on the flange 2 of the base 1. This cleaning tank 3 has large and small rectangular cylinder parts 4a arranged in a similar manner.
s4b, and a rectangular ring plate 5 which is integrally provided at the lower part between these cylindrical parts 4a and 4b and comes into contact with the flange 2 of the base 1. Further, between the top surface of the base 1 and the bottom surface of the cleaning tank 3, a rectangular tantalum diaphragm 6 having a thickness of 0.2 mm, for example, is arranged. The cleaning tank 3 is fixed to the base 1 by a plurality of bolts 7 inserted into the ring plate 5, the diaphragm 6, and the flange 2, and nuts 8 screwed onto these bolts 7. , the peripheral edge of the diaphragm 6 is held and fixed by the ring plate 5 and the flange 2. Note that gaskets 9a and 9b are interposed between the diaphragm 6 and the flange 2 and between the diaphragm 6 and the ring plate 5, respectively, for liquid-tightly fixing the cleaning tank 3 to the base 1. On the surface of the diaphragm 6 on the side of the base 1, as shown in FIG. 2, for example, 14 hexagonal vibrators 1o are arranged and attached in close proximity to each other. These vibrators 10 are connected to an oscillator 13 that oscillates a high frequency of, for example, 800 kHz via a lead plate 11 and a cable 12, and sweeps with a width of ±2.5 kHz.
It is connected to the.

a small-diameter cylindrical portion 4 whose bottom is the vibration plate 6 of the cleaning tank 3;
A cleaning liquid 14 made of, for example, hydrogen peroxide, ammonia, and ultrapure water is contained in the chamber b. The small diameter cylindrical portion 4
A plurality of notches are formed at the upper end of b to allow the cleaning liquid to overflow. Further, the small diameter cylindrical portion 4b
A cleaning liquid supply pipe 15 inserted through the large-diameter cylindrical portion 4a is connected to the side wall of the cylindrical portion 4b. A discharge pipe (not shown) is connected to discharge the cleaning liquid to the outside through the annular space between each cylinder portion 4a, 4b.

According to such a configuration, the cassette 17 containing a plurality of silicon wafers 16 as objects to be processed is transferred to the cleaning tank 3.
After being immersed in the cleaning liquid 14 in the tank, while supplying fresh cleaning liquid from the supply pipe 15 to the cleaning tank 3, a high frequency of 800 kHz is applied from the oscillator 13 to the multiple hexagonal vibrators 10 through the cable 12 and lead plate 11. Along with giving ±
When sweeping under the condition of 2.5 kHz, even if there are variations in vibration characteristics between each vibrator 10, the swept frequency matches the vibration characteristics of each vibrator 10, so the swept frequency can be swept with an extremely short time difference. All of the vibrators 10 vibrate well, and the vibration efficiency of the vibrator 10 at a specific position is prevented from becoming low due to variations in vibration characteristics among the vibrators 10. In other words, the vibration characteristics of the vibrator vary depending on its shape, film thickness, etc. (normally ±1.5% of the set vibration frequency)
However, by using the oscillator 13 having the above-mentioned function of sweeping in a width of ±2.5 kHz, it is possible to eliminate the decrease in vibration efficiency due to variations in vibration characteristics among the individual vibrators 10. Due to the efficient perturbation of each vibrator 10 and the fact that the diaphragm 6 is made of extremely thin tantalum,
The diaphragm 6 to which each vibrator 10 is attached resonates well and vibrates, generating approximately the same high frequency of 800 kHz as described above. As a result, the acceleration within the cleaning liquid 14 that comes into contact with the diaphragm 6 is proportional to the square of the frequency, so approximately 2.5
The surface of each wafer 16 in the cassette 17 is scribed with an acceleration of X105 G, which is 2b times the gravity. Therefore,
Since even minute contaminants down to 0.3 μm attached to the surface of each wafer 16 can be removed, the surface of each wafer 16 can be highly cleaned. However, since each wafer 16 is scribed by the acceleration over the entire area including the vicinity of the contact portion with the cassette 17, the entire wafer 16 can be uniformly cleaned.

Furthermore, since the 800 kHz frequency generated by the diaphragm 1o does not cause cavitation in the cleaning liquid 14, damage to the surface of each wafer housed in the cassette 17 can be prevented.

Furthermore, if the vibrators 10 have a hexagonal shape and are arranged and attached close to each other on the tantalum diaphragm 6, the efficiency of vibration conversion from each vibrator 1o to the diaphragm 6 can be increased. This makes it possible to further effectively remove contaminants from the surface of the wafer 16.

In the above embodiment, the cleaning tank has a double cylindrical shape, but for example, a ring-shaped flange is attached to the lower end of the cylindrical part, which is the main body of the cleaning tank, and a dish-shaped container is installed at the upper part to receive the overflowing cleaning liquid. It is also possible to have a structure in which

In the above embodiments, the cleaning tank is made of polypropylene, but it is not limited thereto. For example, it may be formed of stainless steel lined with fluororesin or ceramics such as alumina.

In the above embodiment, the diaphragm was provided at the bottom of the cleaning tank, but the diaphragm may be provided at the side wall of the cleaning tank.

In the above embodiment, a hexagonal vibrator is used, but the vibrator is not limited to this, and other shapes such as a square or a triangle may also be used. Of course, the number of sheets is not limited to 14 either.

In the above example, a cleaning solution consisting of hydrogen peroxide, ammonia and ultrapure water was used.
Other cleaning solutions may be used, such as those consisting of ultrapure water.

In the above embodiments, an example was explained in which the present invention was applied to cleaning at the wafer stage, but the present invention can be similarly applied to the process of forming elements on the wafer surface. In addition to silicon wafers, we also offer ■-■ group compound semiconductor wafers, AI! It can be similarly applied to cleaning metal magnetic disks such as.

[Effects of the Invention] As detailed above, the cleaning apparatus of the present invention can extremely effectively remove minute contaminants down to 0.3 μm attached to the surface of a workpiece such as a wafer, and moreover, This method has remarkable effects such as being able to prevent damage to objects due to cavitation and, in turn, making it possible to obtain objects to be treated with high cleanliness and no defects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a cleaning device showing an embodiment of the present invention, and FIG. 2 is a plan view showing the shape and arrangement of vibrators in the cleaning device of FIG. DESCRIPTION OF SYMBOLS 1... Base, 3... Cleaning tank, 6... Tantalum diaphragm, 10... Vibrator, 13... Bomber, 14...
-Cleaning liquid, 16... silicon wafer, 17... cassette. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A cleaning tank containing a cleaning solution, a diaphragm with a thickness of 0.1 to 0.5 mm made of a high-melting point metal and placed on the bottom or side wall of the cleaning tank so as to be in direct contact with the cleaning solution, and this diaphragm. A plurality of vibrators are attached to the outer surface of the device and vibrated at a high frequency of 400 to 1000 kHz, and these vibrators are vibrated at the frequency and swept within a range of ±100 kHz or less around the set frequency. A cleaning device characterized by comprising an oscillator.